1. Field of the Invention
This invention relates to improvements in a solid-state imaging device in which photoelectric elements and scanners for selecting the elements are integrated on an identical semiconductor substrate.
2. Description of the Prior Art
As an example of a solid-state imaging device, there has been one in which only scanners and groups of switches connected thereto are arrayed on a semiconductor substrate and are overlaid with a thin photoconductive film for the photoelectric conversion function. Owing to the double-layer structure in which photoelectric elements are formed over the scanners and the groups of switches, this device enhances the packaging density of picture elements (in other words, the resolving power) and the light receiving efficiency more and is therefore expected as a solid-state imaging device in the future. Examples of the solid-state imaging device of this type are disclosed in Japanese Published Unexamined Patent Application No. 51-10715 (filed July 5, 1974); INTERNATIONAL ELECTRON DEVICES MEETING, December 1979, pp. 134-136; etc. FIG. 1 shows a construction for explaining the principle of the device. In the figure, numeral 1 designates a horizontal scanner which turns "on" and "off" horizontal position selecting switches 3, numeral 2 a vertical scanner which turns "on" and "off" vertical position selecting switches 4, numeral 5 a photoelectric element which utilizes a thin photoconductive film, numeral 6 a supply voltage terminal which serves to drive the photoelectric elements 5, numerals 10-1 and 10-2 signal output lines, and letter R a resistor, FIG. 2 shows a sectional structure of a photoelectric conversion region in FIG. 1, in which numeral 5' indicates a thin photoconductive film, numeral 6' indicates a supply voltage applied through a transparent electrode 7, numeral 4' indicates a vertical switch and numeral 8 an insulating film. Numeral 11 indicates a semiconductor substrate, numeral 12 indicates a gate electrode, and numeral 13 indicates an electrode (of, for example, Al) which is held in ohmic contact with one and 9 (a diffused region formed by the use of an impurity opposite in the conductivity type to the substrate 11) of the switch 4'. When an optical image is formed on the thin photoconductive film through a lens, the resistance value of the photoconductive film varies depending upon the light intensities of the optical image. A voltage variation corresponding to the optical image appears at the end 9 of the vertical switch 4 (4'), and this variation is derived as a video signal from an output terminal OUT through the signal output lines 10-1 and 10-2. Shown at numeral 16 is an impurity diffused region which has the same conductivity type as that of the region 9 and which is connected to the signal output line 10-1.